The invention pertains generally to electronic fuel injection systems and is more particularly directed to fuel delivery metering apparatus for such systems.
The majority of automobiles being built today have fuel systems which are either controlled by means of a carburetor or a fuel injection system. The system being described herein is calculated to combine the advantages of both systems and either solve or ameliorate many of the inherent problems of the two systems.
In the case of a carburetor, while it has an advantage of low cost and low operating fuel pressure, there are many undesirable characteristics inherent to the use of a carburetor. For example, the operation of a carburetor requires a continuous flow of fuel, the quantity of fuel being determined on the position of the throttle. It has been found that the fuel is not properly atomized and entrained in the air flow through the throat of the carburetor. Without proper atomization, the fuel distribution to the various cylinders is uneven thereby causing a rich or lean mixture from one cylinder to another. This situation increases the objectionable emissions from the particular cylinder which is too rich or too lean relative to stoichiometric. Also, relative to a fuel injection system, the carburetted system is inherently inaccurate in its fuel control whereby all of the cylinders may be operating at a point different from optimum.
Further, carburetted systems are typically operated in an open loop mode of operation. With this type of operation, the output of the engine exhaust system is not sensed to determine the quality of combustion which is occurring in the engine. Under these circumstances, the optimum air/fuel ratio is not achieved and higher emission levels are again experienced.
The shortcomings of a carburetted system have been somewhat eliminated by certain fuel injection systems on the market. With a fuel injection system, the fuel management is provided with a rather precise control of the fuel being fed to the engine which results in improved driveability without unwanted surges, lower emission levels, convenient changes of the calibration of the system, and the system may be operated in a closed loop mode of operation.
As the importance of electronic fuel injection systems continues to increase because of their adaptability for economy fuel metering and emission control, the actual valving devices or fuel injectors of such systems are becoming more critical to the operation of such systems as the limiting factors of operation.
The preferred valving device for the modern internal combustion engine injection system is the electromagnetically operated solenoid type. The solenoid valve is relatively fast acting and accurate while being compatible and easily interfaced with modern electronic air/fuel ratio controllers. Controlling the opening and closing times of the injectors electronically provides a powerful technique for adapting the air/fuel ratio with respect to a program or prestored schedule to control emissions. Normally, the electromagnetic injectors are either specifically designed for either single point or multipoint operation.
In the single point operation, usually one injector is configured to deliver fuel at one general distribution point, conventionally the air induction bore of a throttle body connecting to a plane of a manifold arrangement. A fast acting high capacity solenoid valve is needed in this arrangement since the injector must work twice as fast as in a multipoint arrangement while delivering twice the fuel for an eight cylinder engine. An advantageous single point system specially adapted to a dual plane manifold arrangement is disclosed in issued U.S. Pat. No. 4,142,683 entitled "Electric Fuel Injection Valve," in the name of G. L. Casey et al. which is commonly assigned. The disclosure of Casey is expressly incorporated by reference herein.
In a multipoint system, a plurality of points are injected in a localized manner, for example each individual cylinder of a multi-cylinder engine. A fuel rail or fuel manifold is required to supply these systems at relatively high pressures. This high pressure fuel enters one end of the injector and passes through a restrictive passage to where it is metered from an exit orifice into the vicinity of the intake valve of the cylinder. A multipoint fuel injection system of this type is illustrated in a U.S. Pat. No. 3,788,287 issued to Falen et al. The disclosure of Falen is expressly incorporated herein by reference.
With a multipoint system, there are problems involved in the hot starting of the automobile and hot fuel handling due to the fact that the injectors are positioned very close to the high heat areas of the engine, as are the fuel lines feeding the injectors. This creates vaporization of the fuel resulting in a low quantity of fuel being injected per pulse to create a lean air/fuel ratio. Further, the multipoint fuel injection system requires the high pressure fuel system with the inherent sealing problems and the cost of a high pressure pump.
It would therefore be desirable to provide an injector that could interchangeably be utilized in either single or multipoint systems. Also, a rapid substitution injector for either type system would be a very positive advantage of such a valve.